Mass air flow meter issues???

I have an 84 633CSi. I will start it and the engine would turn over, but when I let go of the key the car would die. I checked the fuel system was working fine, I put in a new alternator, also tried a used '85 mass air flow meter off an E28, but still the same thing. Any suggestion would be appreciated.

Since the 85 535i AFM and the 84 633 AFM are different, I wouldn't see this as a proof of anything. How did you check the fuel system? Why a new alternator? Anyhow, I will have to check the wiring diagrams on this one, but I suspect that the ECU has power on crank, but that the power in run circuit is interrupted by a blown fuse or a relay issue. It is also possible that the timing sensor is bad and that the car is relying on the TDC sensor to run in crank but can't keep going when the starter is off.